Mobile devices engage in wireless communication over radio frequency (RF) spectrums known as channels. When initiating a wireless connection with a base station of a telecommunication network, the mobile device may listen at a given channel for downlink communications. As used herein, a downlink communication is a transmission from a base station to a mobile device. The mobile device may also receive an assignment of a subcarrier from the base station. The subcarrier is a part of a channel. For example, if a channel comprises an RF spectrum, the subcarrier is a part of that spectrum allocated for uplink communications of the mobile device. As used herein, an uplink communication is a transmission from a mobile device to a base station.
Both mobile devices and base stations incorporate filters in their radios to prevent interference with other channels. Different types of filters have different limitations, some with sharper roll-offs than others. In general, the sharper the roll-off of a filter, the less likely it will be that transmissions from a radio with that filter will interfere with an adjacent channel. Adjacent channel interference is also dealt with through the use of guardbands. Guardbands are reserved parts of an RF spectrum comprising a channel at each end of that RF spectrum. Base stations will not use or assign carriers or subcarriers in the guardbands. Thus, even when a mobile device or base station has a poor roll-off, no adjacent channel interference will occur. As filters continue to improve, however, the size of the guardbands may be needlessly large, resulting in underutilized RF spectrum and artificial congestion.